Just some suggestions as nobody also has chimed in, I think it would look cool and help with fine tuning to put on 4 trim tabs 2 on each side for a scale look. amd like you said I'd run a flex line out the bottom with an in line rudder.
This should give you plenty of room to work with
http://www.hobbyking.com/hobbyking/s...r_Cooling.html
Have any pictures?